This removes libcontainer/cgroups packages and starts
using those from github.com/opencontainers/cgroups repo.
Mostly generated by:
git rm -f libcontainer/cgroups
find . -type f -name "*.go" -exec sed -i \
's|github.com/opencontainers/runc/libcontainer/cgroups|github.com/opencontainers/cgroups|g' \
{} +
go get github.com/opencontainers/cgroups@v0.0.1
make vendor
gofumpt -w .
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>